A planar magnetic is a low profile transformer or
inductor utilizing planar windings instead of the traditional
windings made of Cu-wires. In this paper, the important factors
for planar transformer design including winding loss, core loss,
leakage inductance and stray capacitance have been investigated
individually. The tradeoffs among these factors have to be
analyzed in order to achieve optimal parameters. Combined
with a certain application, four typical winding arrangements
have been compared to illustrate each their advantages and
disadvantages. An improved interleaving structure with optimal
behaviors is proposed, which constructs the top layer paralleling
with the bottom layer and then in series with the other turns of
the primary so that a lower magneto motive force (MMF) ratio
m can be obtained as well as minimized AC resistance, leakage
inductance and even stray capacitance. A 1.2-kW full-bridge
DC-DC converter prototype employing the improved planar
transformer structure has been constructed, over 96%
efficiency is achieved and a 2.7% improvement compared to the
non-interleaving structure is obtained.

Conference

Bibliographical note

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